As an information input device including a panel member having an information input function, a device having a touch panel disposed on a liquid crystal display is being widely used. In the case of a digital camera having a liquid crystal monitor, there is known one configured such that on an upper face of the liquid crystal monitor there is disposed a panel member capable of detecting a contact position and a press force, so that in accordance with the strengths of the press at the time of contact, different instructions are given (see e.g. Patent Document 1, FIG. 25).
In a pressure detection unit 20 to be mounted on the information input device described above, for example, as shown in FIG. 26, between the first substrate 21 and the second substrate 22, from the side of the second substrate 22, there are arranged a second electrode 22A, a carbon layer 22B, a pressure sensitive ink layer 23a and a first electrode 21A in this mentioned order, so that the detection unit determines a pressure when the touch panel or the like is pressed down, and information is instructed for its input in accordance with a determined pressure value.